Or midquel, actually, or whatever you want to call "a book that takes place in the middle of a televised story". Like "The Story of Martha" for the Year That Never Was. Anyway, the book, entitled "Tales of Trenzalore", will be published by BBC Digital 27 Feb, 2014. Four authors and four stories - "Let it Snow", by Justin Richards, George Mann's "An Apple a Day", Paul Finch has written one called "Strangers in the Outland", and finally there's one by Mark Morris called "The Dreaming". Amazon is selling it for the Kindle for £2.49.

Here's the description: 

"As it had been foretold, the armies of the Universe gathered at Trenzalore. Only one thing stood between the planet and destruction - the Doctor. For nine hundred years, he defended the planet, and the tiny town of Christmas, against the forces that would destroy it."

"He never knew how long he could keep the peace. He never knew what creatures would emerge from the snowy night to threaten him next. He knew only that at the end he would die on Trenzalore."

"Some of what happened during those terrible years is well documented. But most of it remains shrouded in mystery and darkness.

"Until now."

"This is a glimpse of just some of the terrors the people faced, the monstrous threats the Doctor defeated. These are the tales of the monsters who found themselves afraid - and of the one man who was not."